Certain products dispensed by aerosol valves have a high solid and/or resin content formulation susceptible to clogging the aerosol valve and actuator after use, for example paint and certain hairsprays and antiperspirants. It is well known that the users of paint in aerosol containers are instructed to invert the container after use and operate the valve actuator until a clear spray of propellant issues the nozzle, thus indicating that substantial paint residue does not remain in the valve and actuator to clog and render inoperable the sprayer. In the process, significant propellant loss occurs. In addition, traditional paint valve systems do not lend themselves to the use of mechanical break-up inserts in the nozzle, such inserts having small channels which easily clog. The use of such inserts would be desirable to improve product spray patterns.
Aerosol valve systems have been conceived to partially obviate the above problems by providing self-purging (automatic purging) capabilities. However, such systems are expensive, involve multiple springs, require excessive force to open, do not function adequately, and/or are difficult to manufacture or assemble. An example of a multiple spring system is shown in U.S. Pat. No. 3,749,291 (Prussin, Mason).
Aerosol valves generally are operated by metal return springs that contact and act directly upon the valve stem body to return it to its closed position after actuation of the valve ceases. The spring has a significant upward force, thus requiring a significant downward force by the user to open and maintain the aerosol open. The metal return spring also provides well-known corrosion problems with certain products, adds significant cost to the aerosol valve assembly, and requires a separate assembly operation. Plastic return springs have been suggested as an alternative, but can be difficult and expensive to mold, require a significant user force to open and maintain open, and are more subject to failure than metal return springs.
Various attempts have been made to eliminate valve return springs, whether metal or plastic. Most such attempts have been inadequate and/or overly complicated in concept and construction. One successful attempt is shown in U.S. Pat. No. 6,588,628 (Abplanalp, Bayer, Flynn) but it, as well as the other various attempts, do not provide or suggest a means for automatic purging of the valve of paint and other high solid/resin content products as discussed above.